Mine roof supports

ABSTRACT

An hydraulically powered chock leg adapted to support or to form part of a support means for a mine roof accommodates the natural tendency for relative movement between the roof and floor of the mine working by being movable from a predetermined position to a position of maximum allowed movement, and is biased towards the predetermined position by a co-axial coil spring surrounding a lower portion of a cylinder of a cylinder and piston arrangement, a first annulus on which said coil spring bears, a first guide sleeve co-axial with said cylinder, surrounding said lower portion thereof and attached to said first annulus, a base plate assembly engaged by said first annulus, the first guide sleeve and its annulus being displaceable with respect to said cylinder, a second annulus on which said coil spring also bears, a second guide sleeve also co-axial with said cylinder, surrounding said upper portion thereof and attached to said second annulus, the second guide sleeve and its annulus also being displaceable with respect to said cylinder, said first guide sleeve being movable towards the second guide sleeve up to an amount determined by the closing of an initial axial gap, a closure cap screwed on to said cylinder, and a support member in said base plate assembly, said cylinder sitting on said support member via mutually intergaging concave/conex support surfaces.

United States Patent Primary Examiner--William H. Schultz Attorney-Allan M. Lowe et al,

11] I 3,738,605 s ith June 12, 1973 [54] MINE ROOF SUPPORTS [75] Inventor: David Beaumont Smith, Wakefield, ABSTRACT Yorkshire, Englan An hydraulically powered chock leg adapted to support e i or to form part of a su port means for a mine roof ac- [73] Asslgnee' g g sg sutchffe wlld Limited commodates the natural tendency for relative moveg ment between the roof and floor of the mine working [22] Filed: Oct- 27, 19 1 by being movable from a predetermined position to a position of maximum allowed movement, and is biased [21] Appl' 193346 towards the predetermined position by a co-axial coil spring surrounding a lower portion of a cylinder of a [30] Foreign Application Pr ty Data cylinder and piston arrangement, a first annulus on Oct. 2, 1970 Great Britain 46,858/70 which said coil spring bears, a first guide sleeve co-axial with said cylinder, surrounding said lower portion [52] US. Cl. 248/354 H, 248/357 thereof and attached to said first annulus, a base plate [51] Int. Cl E2lb 15/30 assembly engaged by said first annulus, the first guide [58] Field of Search 248/160, 354 H, 354 R, sleeve and its annulus being displaceable with respect 248/354 S, 356, 357 to said cylinder, a second annulus on which said coil spring also bears, a second guide sleeve also co-axial [56] References Cited with said cylinder, surrounding said upper portion UNITED STATES PATENTS thereof and attached to said second annulus, the sec- 6 C ff 248/160 x 0nd guide sleeve and its annulus also being displaceable 159042l gqgg man 248,357 X with respect to said cylinder, said first guide sleeve 3133831? 611% eiifiiiiiiiiiiii 248,356 being meveele the guide p 3:48 l 1573 12/1969 Else et al. 248/357 an amoulm determmed y s o g 3 821a! a a c osure ca screwe onto sa: 0 m er, an a FOREIGN PATENTS OR APPLICATIONS Eugport member iii said base plate assembly, said cylin- 785,470 10/1957 Great Britain 248/357 der sitting on said support member via mutually intergaging concave/conex support surfaces.

15 Claims, 4 Drawing Figures MINE ROOF SUPPORTS This invention relates to hydraulically powered chock legs consisting basically of a piston and cylinder adapted to support, or to form part of support means for a mine roof, the chock leg being set between the floor and roof of a mine working, as usual with a floor engaging base plate assembly and a roof engaging bar(s)' or cap.

It is known to set a chock leg between the roof and floor of a mine working and to accommodate the natural tendency for relative movement between floor and roof as the mineral face is being advanced by allowing the chock legs to pivot, within limits, about their base plate assemblies whether the chock legs are initially set vertically or initially set in a slightly forwardly or rearwardly inclined position e.g., 3.

It is also known, with chock legs capable of accommodating the above described roof movement, to provide a spring device in the piston of the chock leg to return the chock leg to its initial position when the chock leg is released from the roof in whatever position it has been moved to by the roof or floor and it is to a chock leg of this self-returning or self-levelling type to which the invention is concerned.

According to the present invention, an hydraulically powered chock leg comprises a cylinder adapted, in use, to be located adjacent the floor of the mine working, and a piston, the free end of which is adapted, in

use, to be located towards the roof of the mine working with a lower portion of the cylinder surrounded by a co-axial coil spring which bears, at the end of the cylinder remote from the piston, on a first annulus that is adapted to engage a portion of a base plate assembly and is attached to a first guide sleeve co-axial with the cylinder and surrounding a portion thereof and being displaceable with respect to the cylinder, the spring also bearing at its other end on a second annulus attached to a second guide sleeve also co-axial with the cylinder and surrounding another portion thereof and displaceable with respect to the cylinder, the first guide sleeve being movable towards the second guide sleeve up to an amount determined by the closing of an initial axial gap, under the influence of the engagement of the first annulus and th portion of the base plate assembly and a closure cap screwed on to the upper end of the cylinder to precompress the spring, to displace the second guide sleeve and to set the axial gap, while the lower end of the cylinder is closed by an end wall having a convex indentation or a concave projection adapted to sit on a concave or convex support surface of the base plate assembly, to accommodate movement of the chock leg.

Thus, in use, when the chock leg is displaced out of its predetermined position the spring is further compressed by movement of the first annulus along the cylinder towards the second annulus so that upon release of the chock leg from the roof the spring automatically returns the chock leg to its predetermined initial position, the axial gap being progressively closed as the chock leg is displaced until it becomes completely closed when the chock leg attains its maximum allowed movement.

The two guide sleeves may be of similar diameter or of dissimilar diameter.

For similar diameter guide sleeves, the axial gap is formed between adjacent ends of the two guide sleeves so that when the chock leg attains its. maximum allowed movement the two sleeves abut one another.

For dissimilar diameter guide sleeves, the latter telescope into one another as the chock leg is displaced out of its predetermined position and the axial gap is formed by the end of one guide sleeve and the annulus of the other guide sleeve which abut one another when the chock leg attains its maximum allowed movement. Preferably it is the second guide sleeve that abuts the first annulus. This construction gives the added advantage that, with the guide sleeve welded to its annulus, the guide sleeve shears from the annulus rather than V the chock leg becoming damaged should there be any excessive movement between the roof and floor.

Also, for similar diameter guide sleeves, the second annulus preferably carries a cover sleeve that surrounds the spring between which cover sleeve and a portion of the base plate assembly may be located a flexible seal.

A further feature of the invention is that the cylinder end wall is preferably located on the opposite side of a plate of the base plate assembly to the remainder of the chock leg, the remainder passing through an aperture in the plate.

Thus, either the plate may be an integral part of the base plate assembly or the plate may simply sit on the base plate assembly and be detachably secured thereto, but for either of these arrangements, the aperture has a chamfered edge (preferably arcuately chamfered) with corresponding surfaces for engaging with the edge carried by the chock leg, so that those corresponding surfaces ride along the chamfered edge during movement of the chock leg between its predetermined position and a displaced position caused by relative movement between floor and roof.

The corresponding surfaces on the chock leg may be provided either by suitably shaping the end wall or alternatively they may be provided on a bearing sleeve carried by the lower end of the chock leg, which bearing sleeve may sit on a peripheral flange of the end wall.

The concave or convex support surface is formed in or on a support member welded to, or otherwise secured in the base plate assembly.

With a chock leg incorporating any of the features outlined above and with the chock leg set in its prede termined position i.e., vertical or generally vertical, pivotal movement of the chock leg due to relative movement between the roof and floor about the convex/concave surfaces lifts one side of the first annulus from contact with theapertured plate while the opposite side of the first annulus contacts the apertured plate at or adjacent its lower out-er corner, for which purpose such corner may be radiused or chamfered, this movement having the effect of sliding the first annulus and its guide sleeve along the cylinder away from the end wall, thereby effecting further compression of the spring and thereby providing a still greater force tending to resist relative movement between the floor and roof but mainly to return the chock leg to its predetermined position when the chock leg is released from the roof.

The chock legs according to the invention are of course usually to be incorporated as part of a hydraulically powered self-advancing mine roof support. However, where several such chock legs are used in a single roof support e.g., a support having two forward legs and four rearward legs, all arranged in pairs, it is possible to dispense with springs on some of the legs e.g., the pair of centre legs and to rely on the realignment reaction of the legs forwardly and rearwardly of these centre legs via. the interconnecting roof bar, to return the centre legs into their predetermined position.

The invention will now be described, in greater detail, by way of examples, with reference to the accompanying drawings in which:

FIG. 1 is a sectional side elevation of a first embodiment of chock leg according to the invention shown in its predetermined (vertical) position;

FIG. 2 corresponds to FIG. 1 but shows the chock leg in the position of its maximum allowed movement;

FIG. 3 is a sectional side elevation of a second embodiment of chock leg according to the invention shown in its predetermined (vertical) position; and,

FIG. 4 corresponds to FIG. 3 but shows the chock leg in the position of its maximum allowed movement.

In the embodiment of FIGS. 1 and 2, an hydraulically powered chock leg is indicated generally at 1 and comprises a cylinder 2 adapted in use to be located adjacent the floor of a mine working and a piston 3 having a piston head 4 located within the cylinder 2 and a free end 5 which is adapted, in use, to be located towards the roof of the mine working. In the drawings, the piston head 4 is shown at an upper end 6 of the cylinder 2 i.e., the chock leg 1 is shown in its fully extended position. A lower end 7 of the cylinder 2 is closed by an end wall 8 and is co-axially surrounded by a first guide sleeve 9 slidable on the lower end 7 and welded to a first annulus 10. The upper end 6 of the cylinder 2 is co-axially surrounded by a second guide sleeve 11 welded to a second annulus 12, a coil spring 13 being compressed between an underside 14 of the second annulus 12 and an upper side 15 of the first annulus 10. The upper end 6 of the cylinder 2 is threaded externally at 63 to receive a closure cap 16 which is capable of adjusting the position of the second annulus 12 with respect to the cylinder 2 and hence the pre-compression of the spring 13, while the lower end 7 of the cylinder 2 is supported in and by a base plate assembly 17.

In this embodiment the first and second guide sleeves 9 and 11 are of the same diameter and the cap 16 is so adjusted that an initial axial gap 18 is set between an upper end 19 of the first co-axial sleeve 9 and a lower end 20 of the second co-axial sleeve 11. The end wall 8 is provided with a convex indentation 21 and is arcuately shaped at 22 to correspond with an arcuate chamfer 23 around an aperture 24 in a plate 25 of the base plate assembly 17, on which plate 25 seats an underside 26 of the first annulus 10, the remainder of the chock leg projecting through the aperture 24, while a portion of the end wall 8 including the indentation 21, projects beneath the plate 25 and seats on a concave indentation 27 of a support member 28 welded on the base plate assembly 17. The second annulus 12 carries a cover sleeve 29 that surrounds the spring 13 between which cover sleeve and the plate 25 is a flexible seal 30.

FIG. 1 shows the chock leg in it predetermined position i.e. vertical. FIG. 2 shows the chock leg of FIG. 1 after the roof has moved from right to left considering that Figure. It will be observed that at one side 31 of the first annulus the underside 26 has been lifted from contact with the plate 25 while at the opposite side 32 of the annulus, contact between the underside 26 and the plate 25 is at or adjacent a lower outer comer 33 of the annulus 10, which corner is chamfered. Simultaneously the gap 18 has been progressively closed and the spring 13 further compressed by movement of the first guide sleeve 9 and its annulus 10 along the lower end 7 of the cylinder 2 unti the chock leg attains its maximum allowed movement (about 13 from vertical) when the upper end of the first guide sleeve 9 abuts the lower end of the second guide sleeve 11, though this situation is not often attained. When the chock leg of the invention is released from the roof the reaction of the spring 13 has the effect of urging the chock leg back to its predetermined position by acting through the first annulus 10 on the plate 25, the gap 18 progressively reopening as this return movement takes place.

In the embodiment of FIGS. 3 and 4, an hydraulically powered chock leg is indicated generally at 1A and comprises a cylinder 2A adapted in use to be located adjacent the floor of a mine working and a piston 3A having a piston head 4A located within the cylinder 2A and a free end 5A which is adapted, in use, to be located towards the roof of the mine working. In the drawings, the piston head 4A is shown at an upper end 6A of the cylinder 2A, i.e., the chock leg 1A is shown in its fully extended position. A lower end 7A of the cylinder 2A is closed by an end wall 8A and is coaxially surrounded by a first guide sleeve 9A slidable on the lower end 7A and welded to a first annulus 10A. The upper end 6A of the cylinder 2A is co-axially surrounded by a second guide sleeve 11A welded to a second annulus 12A, a coil spring 13A being compressed between an underside 14A of the second annulus 12A and an upper side 15A of the first annulus 10A. The upper end 6A of the cylinder 2A is threaded externally at 6C to receive a closure cap 16A which is capable of adjusting the position of the second annulus 12A with respect to the cylinder 2A and hence the precompression of the spring 13A, while the lower end 7A of the cylinder 2A is supported in and by a base plate assembly 17A.

In this embodiment, the first and second guide sleeves 9A and 11A are of dissimilar diameter, the guide sleeve 9A telescoping inside the second guide sleeve 11A. Again the cap 16A is adjusted along the threaded portion 6C of the upper end 6A of the cylinder 2A to effect precompression of the spring 13A, this compression again being by displacement of the second annulus 12A and simultaneously the second guide sleeve 11A carried by the second annulus 12A is similarly displaced to set the axial gap 18A. However, in this embodiment the gap 18 is between the lower end 20A of the second guide sleeve 11 and the upper side 15A of the first annulus 10. The end wall 8A is provided with a concave projection 34 and with a peripheral flange 35 the projection 34 sitting in a concave indentation 36 of the support member 28A of the base plate assembly 17A. Around the lower end of the cylinder 2A is fitted a bearing sleeve 37 provided at its upper end with arcuate surfaces 38 to co-operate with an arcuate chamfer 39 provided around a circular aperture in a tapered plate 40 (which is equivalent to the plate 25A in the embodiment of FIGS. 1 and 2), the plate 40 sitting on and being detachably secured to the base plate assembly 17A. Between the second guide sleeve 11A and the plate 40 is fastened a flexible seal 30A.

FIG. 3 shows the chock leg in its predetermined position i.e., vertical. FIG. 4 shows the chock leg of FIG. 3 after the roof has moved from right to left considering that Figure. Again, it will be observed that at one side 31A of the first annulus A the underside 26A has been lifted from contact with the plate 40, while at the opposite side 32A of the annulus 10A, contact between the underside 26A and the plate 40 is at or adjacent the lower outer corner 33A of the annulus 10A, which corner is chamfered. Simultaneously the gap 18A has been progressively closed and the spring 13A further compressed by movement of the first guide sleeve 9A and its annulus 10A along the lower end 7A of the cylinder 2A until the upper side A of the annulus 10A abuts the lower end A of the second guide sleeve 11A in which position the chock leg has attained its maximum allowed movement (about 13 from vertical) from its predetermined position.

As before, when the chock leg is released from the roof the spring 13A, by reacting against the second annulus 12A and the first annulus 10A, returns the leg to its predetermined position by acting on the base plate assembly 22A, the gap 18A progressively reopening as this return movement takes place.

What I claim is:

1. An hydraulically powered chock leg comprising a cylinder in use to be located adjacent the floor of the mine working, an end wall closing one end of said cylinder, and a piston extending from the other end of said cylinder and terminating in a free end, said free end being, in use, located towards the roof of the mine working, said cylinder having an upper portion and a lower portion and a co-axial coil spring surrounding a lower portion of a cylinder of a cylinder and piston arrangement, a first annulus on which said coil spring bears, a first guide sleeve co-axial with said cylinder, surrounding said lower portion thereof and attached to said first annulus, a base plate assembly engaged by said first annulus, the first guide sleeve and its annulus being displaceable with respect to'said cylinder, a second annulus on which said coil spring also bears, a second guide sleeve also co-axial with said cylinder, surrounding said upper portion thereof and attached to said second annulus, the second guide sleeve and its annulus also being displaceable with respect to said cylinder, said first guide sleeve being movable towards the second guide sleeve up to an amount determined by the closing of an initial axial gap, a closure cap screwed on to said cylinder, and a support member in said base plate assembly, said cylinder sitting on said support member viamutually intergaging concave/convex support surfaces.

2. A chock leg as claimed in claim 1, wherein said two guide sleeves are of similar diameter.

3. A chock leg as claimedin claim 1, wherein said two guide sleeves are of dissimilar diameter.

4. A chock leg as claimed in claim 1, wherein said axial gap is formed between adjacent ends of said two guide sleeves.

5. A chock leg as claimed in claim 3, wherein said axial gap is formed by an end of one guide sleeve and said annulus of said other guide sleeve.

6. A chock leg as claimed in claim 5, wherein said second guide sleeve abuts said first annulus.

7. A chock leg as claimed in claim 1, comprising a cover sleeve carried by said second annulus and surrounding said coil spring.

8. A chock leg as claimed in claim 7, comprising a flexible seal located between said cover sleeve and said base plate assembly.

9. A chock leg as claimed in claim 1, comprising a plate forming part of said base'plate assembly to one side of which plate is located a part of said chock leg including said cylinder end wall and to the other side of which is located, by passing through an aperture in said plate, the remainder of said chock leg.

10. A chock leg as claimed in claim 9, wherein said plate is an integral part of said base plate assembly.

11. A chock leg as claimed in claim 9, wherein said plate sits on said base plate assembly and is detachably secured thereto.

12. A chock leg as claimed in claim 9, wherein a chamfered edge is provided on said aperture with corresponding surfaces carried by said chock leg.

13. A chock leg as claimed in claim 12, wherein said corresponding surfaces are provided by suitably shaping said end wall. r

14. A chock leg as claimed in claim 1, further comprising a plate forming part of said base plate assembly to one side of which plate is located a part of said chock leg including said upper portion of said cylinder and to the other side of which is located, by passing through an aperture in said plate, the remainder of said chock leg, and a chamfered edge is provided on said aperture with corresponding surfaces carried by said chock leg,

. and a bearing sleeve carried by said chock leg to provide said corresponding surfaces.

15. A chock leg as claimed in claim 14, wherein a peripheral flange is provided on said end wall on which flange said bearing sleeve sits.

I I 8' 1k 

1. An hydraulically powered chock leg comprising a cylinder in use to be located adjacent the floor of the mine working, an end wall closing one end of said cylinder, and a piston extending from the other end of said cylinder and terminating in a free end, said free end being, in use, located towards the roof of the mine working, said cylinder having an upper portion and a lower portion and a co-axial coil spring surrounding a lower portion of a cylinder of a cylinder and piston arrangement, a first annulus on which said coil spring bears, a first guide sleeve co-axial with said cylinder, surrounding said lower portion thereof and attached to said first annulus, a base plate assembly engaged by said first annulus, the first guide sleeve and its annulus being displaceable with respect to said cylinder, a second annulus on which said coil spring also bears, a second guide sleeve also coaxial with said cylinder, surrounding said upper portion thereof and attached to said second annulus, the second guide sleeve and its annulus also being displaceable with respect to said cylinder, said first guide sleeve being movable towards the second guide sleeve up to an amount determined by the closing of an initial axial gap, a closure cap screwed on to said cylinder, and a support member in said base plate assembly, said cylinder sitting on said support member via mutually intergaging concave/convex support surfaces.
 2. A chock leg as claimed in claim 1, wherein said two guide sleeves are of similar diameter.
 3. A chock leg as claimed in claim 1, wherein said two guide sleeves are of dissimilar diameter.
 4. A chock leg as claimed in claim 1, wherein said axial gap is formed between adjacent ends of said two guide sleeves.
 5. A chock leg as claimed in claim 3, wherein said axial gap is formed by an end of one guide sleeve and said annulus of said other guide sleeve.
 6. A chock leg as claimed in claim 5, wherein said second guide sleeve abuts said first annulus.
 7. A chock leg as claimed in claim 1, comprising a cover sleeve carried by said second annulus and surrounding said coil spring.
 8. A chock leg as claimed in claim 7, comprising a flexible seal located between said cover sleeve and said base plate assembly.
 9. A chock leg as claimed in claim 1, comprising a plate forming part of said base plate assembly to one side of which plate is located a part of said chock leg including said cylinder end wall and to the other side of which is located, by passing through an aperture in said plate, the remainder of said chock leg.
 10. A chock leg as claimed in claim 9, wherein said plate is an integral part of said base plate assembly.
 11. A chock leg as claimed in claim 9, wherein said plate sits on said base plate assembly and is detachably secured thereto.
 12. A chock leg as claimed in claim 9, wherein a chamfered edge is provided on said aperture with corresponding surfaces carried by said chock leg.
 13. A chock leg as claiMed in claim 12, wherein said corresponding surfaces are provided by suitably shaping said end wall.
 14. A chock leg as claimed in claim 1, further comprising a plate forming part of said base plate assembly to one side of which plate is located a part of said chock leg including said upper portion of said cylinder and to the other side of which is located, by passing through an aperture in said plate, the remainder of said chock leg, and a chamfered edge is provided on said aperture with corresponding surfaces carried by said chock leg, and a bearing sleeve carried by said chock leg to provide said corresponding surfaces.
 15. A chock leg as claimed in claim 14, wherein a peripheral flange is provided on said end wall on which flange said bearing sleeve sits. 